A Regional Analysis of Low Flow in Tehran Watersheds

Analysis of low flow is one of the important considerations , in any water resource project-Meanwhile ,as a general idea it seems that flow control is more important than drought mitigation but, it is necessary .to pay more attention to drought problem in future projects. In this paper, available data for 12,selected watersheds were analyzed and low of 30 day with different return periods were calculated for each set of flow. data. Also, hydroclmatic and .geomorphologic. parameters "were considered to obtain the most effective factors on low flows which help to separate homogeneity area.
The, most ,effective factors were: area, mean annual precipitation, average weighted infiltration and
average slope of the watershed which illustrate 99/36 percent of variation of data. Then homogeneity areas were identified using cluster analysis.
Meanwhile, regression and low flow indication were obtained using the data Results were compared
with data of 4 control watersheds to evaluate accuracy of the model which showed more efficiency of multivariate regression method as compared to low flow index method in different return periods.